As women, we all have ample hormones to regulate our monthly cycles, pregnancy and breast milk. But does progesterone decrease milk supply? Read on to find out.

Introduction
Hormones are the chemical messengers that govern the body functions and processes. The endocrine glands secrete these hormones in your body, and each hormone has a specific function. They travel in your bloodstream to your organs and tissues, affecting metabolic processes, growth, and development in your body. The two principal hormones in women are estrogen and progesterone, which affect physical characteristics, reproduction, and general health.
What is Progesterone?
Progesterone is a hormone mainly produced by the corpus luteum in the ovary of a female. The adrenal glands also produce it in the body. It plays a vital role in regulating the menstrual cycle and in maintaining pregnancy in its early stages. It is instrumental in preparing the body for conception and in stimulating sexual desire.
Progesterone helps the lining of the uterus to secrete special proteins during the latter half of the menstrual cycle, preparing it to implant and nourish a fertilized egg. During pregnancy, the placenta also produces progesterone, and the level of progesterone is increased during pregnancy. Progesterone is responsible for the development of milk-producing glands in the breast during pregnancy. It inhibits lactation during pregnancy, and the decrease in its levels after delivery acts as a signal for the breasts to begin milk production. If the egg released by the ovary is not fertilized and implanted in the uterus, progesterone levels drop, and menstruation occurs.
Progesterone is also used in oral contraceptives for women to prevent ovulation and hormone replacement therapy to treat the symptoms of menopause.
What are the reasons for increased progesterone levels?
Pregnancy, the presence of cysts in your ovaries, a type of abnormal pregnancy called a hydatidiform mole, congenital adrenal hyperplasia, and certain ovarian tumors that mimic pregnancy symptoms can all cause high levels of progesterone in your body.
Does progesterone affect milk supply?

After delivering your baby, the placenta is expelled, and hence the progesterone levels in your body drop. The level of the hormone estrogen also drops, and this triggers the rise in prolactin levels. Prolactin signals the glands in your breast to begin producing milk.
If you get pregnant while breastfeeding your baby, progesterone levels again begin to increase in your body, affecting your milk supply. Progesterone interferes with prolactin binding to the receptors on the alveolar cells within the breasts, which leads to a suppression of milk production.
Breast milk is stored in small balloon-like structures called alveoli within your breast. The alveoli walls prevent leakage of the milk as the cells in the walls form a tight bond. However, when progesterone levels increase, it causes the cell walls to become permeable, and milk leakage occurs. Hence, the supply of milk to your nursing baby decreases. Along with the dwindling milk supply, the milk also changes in consistency and taste. Milk becomes saltier, and some babies may wean themselves off because of the change in taste and quantity of your milk.
How to control the level of progesterone during breastfeeding?
It is advisable to avoid using hormonal birth control methods that contain progesterone during breastfeeding. Falling pregnant will also cause a rise in progesterone levels and a decrease in milk supply. Hence, pregnancy can be avoided by using suitable non-hormonal contraceptive methods during breastfeeding. However, progestin, a synthetic form of progesterone, can be used for contraception as it does not affect milk production.
It is better to consult a doctor if in doubt about medications containing progesterone.